A University of California at San Francisco professor of biochemistry told CNET today that the Obama administration's claim that full-body scanners pose no health risks to air travelers is in "error."

The administration's defense of the controversial machines, which use X-rays to perform what critics have dubbed naked strip searches, has "many misconceptions, and we will write a careful answer pointing out their errors," said John Sedat, a UCSF professor of biochemistry and biophysics and member of the National Academy of Sciences.

This image of an adult man was taken using a Rapiscan Secure 1000 backscatter X-ray scanner
John Wild (johnwild.info)

"Because four people are working on this, it will not be done in one day," Sedat said.

Earlier this week, the White House's Office of Science and Technology Policy posted a statement saying the X-ray scans are safe because "the issue had been studied extensively for many years" by federal agencies.

That post was a response to a letter (PDF) that Sedat and three other UCSF faculty members sent to White House science advisor John Holdren in April.

Their letter to Holdren said "it appears that real independent safety data do not exist." In addition, the authors say: "There has not been sufficient review of the intermediate and long-term effects of radiation exposure associated with airport scanners. There is good reason to believe that these scanners will increase the risk of cancer to children and other vulnerable populations."

Air travelers over 65 years old are especially susceptible to the "mutagenic effects of the X-rays," they say, as are HIV and cancer patients, children and adolescents, pregnant women, and men (because the X-rays can penetrate skin and put the testicles "at risk for sperm mutagenesis"). Eyes could also be at risk because X-rays can penetrate the cornea.

For its part, the administration rejects any health concerns. A letter last month from the FDA and the Transportation Security Administration responding to the UCSF researchers' concerns says "the potential health risks from a full-body screening with a general-use x-ray security system are miniscule."

Although the X-ray scanners have been used for years, the federal stimulus legislation paid for the deployment of hundreds of the scanners in U.S. airports: they were turned on yesterday in the Orlando airport and have appeared at Dulles airport this week as well. Approximately 68 airports have a total of 373 scanners, the TSA says.

If X-ray scanners were presented to the public as one of many options, the concerns would be muted. But they're being used the primary screening technique.

And anyone hoping to opt-out in favor of a manual pat-down may not like what happens. The TSA quietly changed its procedures a few weeks ago to what it delicately calls "enhanced pat-downs," which involve screeners using their fingers--instead of the backs of their hands--to feel the outlines of male or female genitalia. (See related CNET story.)

About the author

Declan McCullagh is the chief political correspondent for CNET. You can e-mail him or follow him on Twitter as declanm. Declan previously was a reporter for Time and the Washington bureau chief for Wired and wrote the Taking Liberties section and Other People's Money column for CBS News' Web site.
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